1. Field of the Invention
The present invention relates to apparatus, methods, and computer simulations for radiating energy into body tissue and, more particularly, to a separated array of antennas and methods operable for highly selective heating of biological tissue.
2. Background of the Invention
Microwaves and other techniques have been used to necrose malignant, benign, and other types of cells and tissues including glandular and stromal nodules characteristic of benign prostate hyperplasia. Exemplary means for selective heating of body tissues without damaging healthy tissue are taught in U.S. Pat. No. 5,904,709, to Arndt et al., and also U.S. Pat. No. 6,289,249, a parent to the present application and discussed below, which are hereby incorporated herein by reference.
Benign prostatic hypertrophy or hyperplasia (BPH) is one of the most common medical problems experienced by men over 50 years old. Urinary tract obstruction due to prostatic hyperplasia has been recognized since the earliest days of medicine. During healthy operation, the bladder is emptied by way of the urethra, a tube passing through the prostrate gland. The main function of the prostate is to supply fluid for sperm that has been collected in the seminal vesicles. The seminal vesicles are supplied by the vas deferens from the epididymis, a tightly coiled tube next to the testicle that provides for the storage, transmission, and maturation of sperm.
Hyperplastic enlargement of the prostate gland, or enlargement due to abnormal but benign multiplication of the cells thereof, often leads to compression of the urethra thereby resulting in obstruction of the urinary tract. Common symptoms that develop from this condition may include more frequent urination, decrease in urinary flow, nocturia, pain, and discomfort. The incidence of BPH in men over 50 years of age is approximately 50 percent and increases to over 75 percent in men over 80 years of age. Symptoms of urinary obstruction occur most frequently between the ages of 65 and 70 when approximately 65 percent of men in the age group have prostatic enlargement.
When treatment by drug therapy is not sufficiently effective, surgical procedures for treating BPH are available but have potential side effects. General surgical risks apply such as anesthesia related morbidity, hemorrhage, coagulopathies, pulmonary emboli, electrolyte imbalance, and the like. Other problems that may occur from surgical correction include cardiac complications, bladder perforation, incontinence, infection, urethral or bladder neck stricture, retention of prostatic chips, and infertility. Due to the problems of surgery, many or even most patients delay treatment. However, the delay of treatment may lead to other complications including obstructive lesion in the prostate, chronic infection, and the like. Therefore, it is unquestionable that a need exists for improved surgical or non-surgical methods for treating BPH.
U.S. Pat. No. 5,904,709, issued May 18, 1999, to Arndt et al., discloses a method and apparatus for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to the monopole microwave radiator having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.
U.S. Pat. No. 6,289,249 B1, issued Sep. 11, 2001, to Arndt et al., discloses methods, simulations, and apparatus that are highly suitable for treatment of benign prostatic hyperplasia (BPH). A catheter is disclosed that includes a small diameter disk loaded monopole antenna surrounded by fusion material having a high heat of fusion and a melting point preferably at or near body temperature. Microwaves from the antenna heat prostatic tissue to promote necrosing of the prostatic tissue that relieves the pressure of the prostatic tissue against the urethra as the body reabsorbs the necrosed or dead tissue. The fusion material keeps the urethra cool by means of the heat of fusion of the fusion material. This prevents damage to the urethra while the prostatic tissue is necrosed. A computer simulation is provided that can be used to predict the resulting temperature profile produced in the prostatic tissue. By changing the various control features of the catheter and method of applying microwave energy a temperature profile can be predicted and produced that is similar to the temperature profile desired for the particular patient.
More generally, the following patents disclose attempts to solve the above-discussed difficult problems and related problems.
U.S. Pat. No. 5,843,144, issued Dec. 1, 1998, to Rudie et al., discloses a method for treating an individual with diseased prostatic tissue, such as benign prostatic hyperplasia, including inserting a catheter into a urethra to position a microwave antenna located within the catheter adjacent a prostatic region of the urethra. A microwave antenna is then driven within a power range for applying microwave energy substantially continuously to prostatic tissue to heat the prostatic tissue surrounding the microwave antenna at a temperature and for a time period sufficient to cause necrosis of the prostatic tissue.
U.S. Pat. No. 5,843,026, issued Dec. 1, 1998, to Edwards et al., discloses a method and apparatus for delivering controlled heat to perform ablation to treat the benign prosthetic hypertrophy or hyperplasia (BPH). According to the method and the apparatus, the energy is transferred directly into the tissue mass which is to be treated in such a manner as to provide tissue ablation without damage to surrounding tissues. Automatic shut-off occurs when any one of a number of surrounding areas to include the urethra or surrounding mass or the adjacent organs exceed predetermined safe temperature limits. The constant application of the radio frequency energy over a maintained determined time provides a safe procedure which avoids electrosurgical and other invasive operations while providing fast relief to BPH with a short recovery time. The procedure may be accomplished in a doctor's office without the need for hospitalization or surgery.
U.S. Pat. No. 5,830,179, issued Nov. 3, 1998, to Mikus et al., discloses a stent system and method for use in the prostate gland. The stent is made of a shape memory alloy such as nitinol, and has a low temperature martensite state, with a martensite transition temperature below body temperature, and a high temperature austenite state, with an austenite transition temperature at or above body temperature, and a memorized shape in the high temperature austenite state which is a helical coil of diameter large enough to hold the prostatic urethra open. The stent is used to heat the prostate and is left in the prostatic urethra while the prostate heals. After the prostate is substantially healed, the stent is cooled to its martensite state and is easily removed from the urethra.
U.S. Pat. No. 5,800,486, issued Sep. 1, 1998, to Thome et al., discloses an intraurethral catheter which includes a microwave antenna and a cooling lumen structure substantially surrounding the antenna. A cooling balloon partially surrounds the cooling lumens on one side of the catheter adjacent the microwave antenna. The cooling balloon improves wall contact between the catheter and a wall of the urethra to improve cooling of the urethra. The cooling balloon communicates with the cooling lumen structure to permit circulation of cooling fluid through the cooling balloon.
U.S. Pat. No. 5,800,378, issued Sep. 1, 1998, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and a stylet guide for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The total catheter assembly includes a stylet guide lumen communicating with the stylet port and a stylet positioned in said stylet guide lumen for longitudinal movement from the port through intervening tissue to target tissue. The stylet can be an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radio frequency electrode. Preferably, the non-conductive layer is a sleeve which is axially moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue. The stylet can also be a microwave antenna. The catheter can include one or more inflatable balloons located adjacent to the stylet port for anchoring the catheter or dilation. Ultrasound transponders and temperature sensors can be attached to the probe end and/or stylet. The stylet guide can define a stylet path from an axial orientation in the catheter through a curved portion to a lateral orientation at the stylet port.
U.S. Pat. No. 5,755,754, issued May 26, 1998, to Rudie et al., discloses an intraurethral, Foley-type catheter shaft containing a microwave antenna capable of generating a cylindrically symmetrical thermal pattern, within which temperatures are capable of exceeding 45 C. The antenna, which is positioned within the shaft, is surrounded by means within the shaft for absorbing thermal energy conducted by the tissue and asymmetrically absorbing electromagnetic energy emitted by the antenna-a greater amount of electromagnetic energy being absorbed on one side of the shaft. This asymmetrical absorption alters the thermal pattern generated by the microwave antenna, making it cylindrically asymmetrical, which effectively focuses microwave thermal therapy toward undesirous benign tumorous tissue growth of a prostate anterior and lateral to the urethra, and away from healthy tissue posterior to the urethra.
U.S. Pat. No. 5,733,315, issued Mar. 31, 1998, to Burdette et al., discloses an apparatus for applying thermal therapy to a prostate gland, comprising a support tube having a longitudinal central passageway, a power lead channeled through the longitudinal central passageway and an ultrasound crystal disposed around at least part of the support tube. The ultrasound crystal is coupled to the power lead which provides the power to energize the ultrasound crystal and generate ultrasound energy providing thermal therapy to the prostate gland. The ultrasound crystal further includes inactivated portions for reducing ultrasound energy directed to the rectal wall of the patient. A sealant is disposed in contact with the ultrasound crystal allowing vibration necessary for efficient ultrasound energy radiation for the thermal therapy to the prostate gland.
U.S. Pat. No. 5,720,718, issued Feb. 24, 1998, to Rosen et al., discloses a medical probe device comprising a catheter having a stylet guide housing with at least one stylet port in a side thereof and stylet guide means for directing a flexible stylet outward through at least one stylet port and through intervening tissue to targeted tissue. The stylet comprises an electrical central conductor which is enclosed within an insulating or dielectric sleeve surrounded by a conductive layer terminated by an antenna to selectively deliver microwave or radio frequency energy to target tissue. One embodiment includes the electrical conductor being enclosed within a non-conductive sleeve which itself is enclosed within a conductive sleeve in a coaxial cable arrangement to form a microwave transmission line terminated by an antenna. Another embodiment includes a resistive element near the distal end of the stylet which couples the center electrode to an outer conductor to generate joulian heat as electromagnetic energy is applied, such as an RF signal.
U.S. Pat. No. 5,643,335, issued Jul. 1, 1997, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,620,480, issued Apr. 15, 1997, to Eric N. Rudie, discloses a method for treating an individual with benign prostate hyperplasia. The method includes inserting a catheter into a urethra so as to position an energy emitting element located within the catheter adjacent a prostatic region of the urethra. A fluid is circulated within the catheter until the fluid stabilizes at a prechilled temperature. An energy emitting element is then energized sufficient to heat prostatic tissue surrounding the energy emitting element.
U.S. Pat. No. 5,599,294, issued Feb. 4, 1997, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and guide means for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The stylet can be an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radio frequency electrode. Preferably, the non-conductive layer is a sleeve which is axially moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue. The stylet can also be a microwave antenna.
U.S. Pat. No. 5,575,811, issued Nov. 19, 1996, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,509,929, issued Apr. 23, 1996, to Hascoet et al., discloses a urethral probe having a front part and a rear part, and a microwave antenna connected to an external device for generating microwaves. The microwave antenna has its primary active heating part arranged in the urethral probe to be directed onto the prostatic tissue located at least at the level of the bladder neck in the working position. The urethral probe constitutes an essential element of a device for the therapeutic treatment of tissues by thermotherapy, more particularly tissues of the bladder of a human being.
U.S. Pat. No. 5,464,437, issued Nov. 7, 1995, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,413,588, issued May 9, 1995, to Rudie et al., discloses an intraurethral, Foley-type catheter shaft containing a microwave antenna capable of generating a cylindrically symmetrical thermal pattern, within which temperatures are capable of exceeding 45 C. The antenna, which is positioned within the shaft, is surrounded by means within the shaft for absorbing thermal energy conducted by the tissue and asymmetrically absorbing electromagnetic energy emitted by the antenna-a greater amount of electromagnetic energy being absorbed on one side of the shaft. This asymmetrical absorption alters the thermal pattern generated by the microwave antenna, making it cylindrically asymmetrical, which effectively focuses microwave thermal therapy toward undesirous benign tumorous tissue growth of a prostate anterior and lateral to the urethra, and away from healthy tissue posterior to the urethra.
U.S. Pat. No. 5,366,490, issued Nov. 22, 1994, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and guide means for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The stylet can also be a microwave antenna.
U.S. Pat. No. 5,312,392, issued May 17, 1994, to Hofstetter et al., discloses a method of treating benign prostatic hyperplasia employing the steps of inserting a diffusing light guide into a prostrate lobe and providing laser power to the diffusing light guide in order to necrose surrounding tissue. The diffusing light guide can be inserted into the central or lateral prostrate lobes by inserting a needle and a trocar transperineally into the middle of the lateral lobe, removing the trocar, inserting the diffusing light guide, and monitoring the position of the needle, trocar, and diffusing light guide using ultrasound. The diffusing light guide can also be inserted into the central or lateral prostrate lobes transurethrally and positioned with the aid of a urethroscope.
U.S. Pat. No. 4,967,765, issued Nov. 6, 1990, to Turner et al., discloses a urethral inserted applicator for prostate hyperthermia including a multi-tube, balloon type catheter. The catheter includes first and second closed end fluid dry tubes, respectively, for a helical coil antenna type applicator, and a microwave type temperature sensor for measuring the temperature of the prostate tissue, and an open fluid receiving tube. A microwave generator supplies electromagnetic energy to the applicator. A comparator is connected to the temperature sensor and a temperature reference potentiometer for comparing the actual tissue temperature level with a desired temperature level and outputting control signals to the microwave generator for controlling the output to the applicator. The coil type applicator is an elongated coil having a tip end connected to the center conductor of a coaxial cable and an opposite end connected to the outer conductor of the coaxial cable. A sheet or sheath of insulation material covers the coil antenna for insulating the coil from the tissue and the thickness of the sheet may be varied to provide uniform tissue heating along the length of the coil. The balloon of the catheter engages the body's bladder to position the applicator properly during the treatment.
Except for the patents listed above to Arndt et. al, the above cited prior art does not provide an easily fabricated catheter that may be fabricated with variations useful for individual patients, a computer simulation to predict the effect of procedural techniques, and a relatively quick procedure that may be performed in minutes to necrose prostatic tissue while protecting healthy tissue. There is a strong need for treatment techniques that permit accurate pinpointing of heat application within millimeters to necrose selected prostatic tissue while protecting the urethra and other healthy structures. Those skilled in the art have long sought and will appreciate the present invention that addresses these and other problems.